In the processing of hazardous and non-hazardous wastes, such as drilling muds, ship bilge, soils contaminated by oil leaks or spills, tank bottoms, municipal solid wastes and the like, it has been a common practice to simply store the materials in, for example, land fills, lagoons and tanks. It has been long appreciated, however, that such methods of dealing with these materials are unsatisfactory for numerous and self-evident reasons. As a result of this appreciation, many industries have devoted significant time and effort to conducting research for alternative industrial processes that avoid creating the waste materials in the first place, or that limit the production of the waste materials. However, these alternative processes add significantly to the cost of the industrial process, making the overall process less profitable.
As an example, in the extraction of oil and gas from wells, there has been an increase in the use of various polymers, rather than chrome laden sulfonate additives, as widely used in the past. The polymers are more expensive and less effective. Nevertheless, the redeeming value in using these polymers is their ability to be effectively destroyed by incineration. In contrast, chrome-based muds, a known hazardous waste resulting from drilling operations that use chrome additives, when incinerated, not only produce harmful by-products during incineration, such as dioxin and nitrous oxide, but also produce a solid residue that is known to be toxic and to contain leachable metals. Hence, it has been found that destructive procedures for dealing with hazardous waste, such as incineration, are generally expensive and often involve byproducts that, in some circumstances, are as harmful as, or more harmful than, the original wastes.
In another example, materials from tank bottoms, bilge bottoms, and oil-contaminated earth are often incinerated. The incineration process is inherently expensive, because most of these wastes are essentially water. Thus, the wastes must not only be boiled, but also be raised to a proper incineration temperature (1800° F. to 2000° F.) and be held at that temperature for one to two seconds to insure nearly complete combustion. Such a procedure is expensive because additional energy is required to reach the proper temperature. Moreover, it is prone to produce further undesirable by-products as discussed hereinabove, but it also destroys (through oxidation) hydrocarbons that would otherwise be of commercial value if recovered.
Furthermore, disposing of drilling muds is difficult, particularly with known mass volume wet oxidation or even super-critical wet oxidation techniques now being used due, at least in part, to the presence and concentration of metal salts, often in excess of 5000 mg/l. It is well known that these metal salts attack the metal containment vessels used in these techniques and severely damage or destroy the metal containment apparatus of those wet chemistry vessels.
It is also a problem that many wastes are at isolated locations and/or exist in too small quantities to economically warrant a typical fixed base incineration process. As a result, these wastes must be transported at great risk and cost.
There are known processing devices that heat wastes in the absence of oxygen to bake away the hydrocarbons from the water and solids residue, but these devices generally utilize either (1) a batch process or (2) a continuous operation process that provides ineffective methodology or apparatus for the recovery of heat energy. The use of heat energy in the operation is required if the processing device is to be efficiently self sustaining. Such ineffective devices are currently used in the extraction of hydrocarbons from tar sands and oil shales. While these are not wastes per se, their processing is similar in nature to hazardous waste processing except that when compared to most hazardous waste, the sand and shale are usually lower in water and hydrocarbon content percentage to the total solid weight of the materials and the recovery of the hydrocarbon is the primary object of the process.
For example, U.S. Pat. No. 4,280,279 discloses a rotating kiln which introduces feed to an inner drum, wherein outgoing solids pass in counterflow in an exterior, concentric drum. Steam and gases are extracted and condensed separately. This, however, violates the principles of conservation of heat energy in that the coldest materials to be treated are on the interior of the device and the exiting solids, which have the highest temperatures, lose most of their heat to the outside walls of the kiln. No heat energy of the water is conserved at all, nor is the heat energy of the oil extracted. The heat necessary to supply the kiln is derived partially from the combustion of the product itself within the kiln supplemented by a burner discharging into the kiln.
Similarly, U.S. Pat. No. 4,285,773 discloses a cold feed into the interior of a rotating kiln and direct firing within the kiln chamber with extraction of the liquid and oil factions, resulting in the loss of heat therefrom, as well as loss of most of the heat from the solid faction due to its outboard placement.
U.S. Pat. Nos. 4,563,246, 4,583,468 and 4,724,777 all disclose retort devices, which lack the ability of using the heat of vaporization of the liquid water and oil factions to preheat incoming materials. Further, all use peripheral spiral chambers for return flow of solids that are known to often result in flow plugging and poor mixing of the exiting solids as necessary for proper heat extraction.
Therefore, a need exists for a retort apparatus for the baking of a liquid and solid mixture, such as for the processing of hazardous waste, sand tar, oil shale or the like, which has the ability to recover and recycle heat energy, useful by-products, and decontaminated materials from the retort process.